A number of curable, chromium-free first coating agents which are suitable for forming a corrosion protection coating a few micrometers thick on metallic surfaces are known from the prior art. Such first coating agents are conventionally acidic aqueous solutions which bring about an inorganic conversion of the metal surface and a coverage with an organic binder, which is cured after being brought into contact with the first coating agent. In such a method thin inorganic/organic hybrid coatings are obtained which already offer considerable protection against corrosion.
Thus the German laid-open patent application DE 10 2006 039 633 discloses an aqueous curable corrosion protection agent for the first coating of metallic substrates, having a pH in the range from 1 to 3 and containing water and    a) fluoro complex ions of titanium and/or zirconium,    b) at least one corrosion protection pigment,    c) at least one organic polymer which is water-soluble or water-dispersible in the specified pH range and which as such in aqueous solution in a concentration of 50 wt. % has a pH in the range from 1 to 3.
According to the disclosure of DE 10 2006 039 633, in the cured state on metal strip such a corrosion protection agent can already be used as a fully adequate corrosion protection coating. Nevertheless, for an optimal barrier effect against corrosive media and also for the provision of desired mechanical and optical properties of the coated metal strip, a further coating with a curable organic binder system, i.e. the application of further paint systems, is also necessary. An optional second coating is also mentioned in DE 10 2006 039 633, although the properties of adhesion to conventional top coats are not ideal, such that the second coating can easily be penetrated beneath and its functionality compromised.
EP 0 672 467 discloses an intermediate rinsing with a solution of acylated polyvinyl amines for phosphated metal surfaces prior to electrodeposition painting, in order to improve adhesion of the dipping paint to the phosphated metal surface. The use of acylated polyvinyl amines in chromium-free aqueous corrosion protection agents containing an organic binder for the first coating is not mentioned here, nor is the suitability of acylated polyvinyl amines as adhesion promoters for specific organic binder systems.